With advancement in storage technology, the amount of data that can be stored in storage subsystems, which include hard disk drives, disk array systems, and so forth, has increased dramatically. Copies of data in storage subsystems can be maintained for various purposes, including data backup, data mining (in which the data is analyzed to provide a better understanding of the data), and so forth.
There are different types of copies, including snapshots and clones. A snapshot is a point-in-time representation of data. A snapshot contains blocks of data of a source storage volume that have been changed due to one or more write operations (note that unchanged data in the source storage volume is not copied to the snapshot). In response to writes that modify data in the source storage volume, the original data is copied to the snapshot prior to writing to the source storage volume.
Another type of copy is a clone, which contains a full copy of a source storage volume, including data of the source storage volume that has not been modified.
An issue associated with maintaining snapshots and/or clones is that they can be storage space inefficient. Generally, snapshots are more space efficient than clones. However, as a snapshot ages, the storage space utilization of the snapshot also increases, which can lead to increased inefficiency in storage space usage. One reason for the inefficiency of storage space usage is that the snapshots and/or clones may contain a relatively large amount of duplicate data.